1. Field of the Invention
This invention relates in general to sliders for use in magnetic storage devices, and more particularly to slider fabrication methods and slider designs that facilitate fabrication and even more particularly to lapping requirements of slider designs and methods for lapping surfaces on a slider.
2. Description of Prior Art
A typical prior art head and disk system 10 is illustrated in FIG. 1. In operation the magnetic transducer 20 is supported by the suspension 13 as it flies above the disk 16. The magnetic transducer, usually called a xe2x80x9cheadxe2x80x9d or xe2x80x9csliderxe2x80x9d is composed of elements that perform the task of writing magnetic transitions (the write head 23) and reading the magnetic transitions (the read head 12). The electrical signals to and from the read and write heads 12, 23 (collectively xe2x80x9cmagnetic transducer elementsxe2x80x9d) travel along conductive paths (leads) 14 which are attached to or embedded in the suspension 13. Typically there are two electrical contact pads (not shown) each for the read and write heads 12, 23. Wires or leads 14 are connected to these pads and routed in the suspension 13 to the arm electronics (not shown). The disk 16 is attached to a spindle 18 that is driven by a spindle motor 24 to rotate the disk 16. The disk 16 comprises a substrate 26 on which a plurality of thin films 21 are deposited. The thin films 21 include ferromagnetic material in which the write head 23 records the magnetic transitions in which information is encoded. The read head 12 reads magnetic transitions as the disk rotates under the air-bearing surface (ABS) of the magnetic transducer 20.
FIG. 2 is a midline section of one type of prior art magnetic transducer 20 shown prior to lapping. The substrate 43 of the slider is typically a hard durable material. The components of the read head 12 shown are the first shield (S1), surround the sensor 105 which is surrounded by insulation layers 107, 109 and the second shield (P1/S2). This type of magnetic transducer is called a xe2x80x9cmerged headxe2x80x9d because the P1/S2 layer serves as a shield for the read head 12 and a pole piece for the write head 23. The yoke also includes a second pole piece (P2) which connects with P1/S2 at the back. The P2 curves down over coil 37 to confront the P1 across the write gap layer to form the write gap at the air-bearing surface (ABS). The zero throat height (ZTH) is defined as the point where the P2 first touches the gap layer. The sensor 105 includes a magnetoresistive material such as permalloy, but may be a mulitlayered structure containing various layers of ferromagnetic and antiferromagnetic material. The shields and pole pieces are ferromagnetic materials, e.g., NiFe or CoFe. Prior to lapping the materials and structures at the ABS extend beyond the ABS. As illustrated in FIG. 2 the material to the right of the ABS plane is removed by lapping to achieve precise control of the length of the sensor 105 (which is called the xe2x80x9cstripe heightxe2x80x9d) and the distance from the ZTH to the ABS (which is called the xe2x80x9cthroat heightxe2x80x9d). The uncertainty of the saw plane causes variations in the stripe height which are on the order of microns and which would lead to unacceptable variations in magnetic performance is not corrected. Lapping is the process used in the prior art to achieve much tighter stripe height control in the nanometer range.
In the typical process of fabricating thin film magnetic transducers, a large number of transducers are formed simultaneously on a wafer. After the basic structures are formed the wafer may be sawed into quadrants, rows or individual transducers. Further processing may occur at any or all of these stages. Although sawing has been the typical method for separating the wafers into individual sliders, recently reactive ion etching (RIE) or deep reactive ion etching (DRIE) with a flourine containing plasma has been used. The surfaces of the sliders perpendicular to the surface of the wafer that are exposed when the wafers are cut form the air bearing surface (ABS) of the slider.
After lapping, features typically called xe2x80x9crailsxe2x80x9d are formed on the ABS of magnetic transducer 20. The rails have traditionally been used to determine the aerodynamics of the slider and serve as the contact area should the transducer come in contact with the media either while rotating or when stationary.
U.S. Pat. No. 5,321,882 to Zarouri, et al., discloses a process for forming slider air-bearing surfaces one at a time. The sliders are supported by a mechanical backing while being processed sequentially from a column cut from the wafer. In U.S. Pat. No. 6,093,083 to Lackey, a row of sliders is processed while being rigidly bound to a carrier.
Sliders may be lapped in rows, but it may be advantageous to have the individual sliders cut out prior to lapping. Even though the sliders have been separated, it is possible to lap several at one time by attaching them to carrier. The time required to lap sliders is a significant element in the cost of manufacturing; therefore, there is a need to improve production efficiency by reducing lapping time, and achieve an ABS surface with a greater control of flatness parameters.
A process will be described for fabricating sliders with one or more sacrificial structures (extensions) that reduce the amount of time required for lapping to create the air-bearing surface (ABS). In accordance with the present invention the amount of slider material to be removed by lapping is reduced, and additional lapping or polishing steps are eliminated.
Prior to separating individual sliders from a wafer, a mask of material that is not removable by deep reactive ion etching (DRIE) is patterned on the surface of the sliders. The mask outlines a sacrificial extension around portions of the magnetic transducer elements that are nearest the predetermined plane which will become the ABS. The sacrificial extension makes the surface of the slider which will be lapped non-planar. The sacrificial extension extends below the predetermined ABS plane. When the sliders are individually separated by DRIE, the shape of the mask including the sacrificial extension is projected down into and along the slider body. The sacrificial extension covers the thin film elements of the read and write heads. The surface of the slider contains a smaller amount of material (with a high aspect ratio) to be removed by lapping relative to prior art designs which require removal of material on the entire planar surface of the slider. The sacrificial extension reduces the amount material to be removed by lapping while maintaining the ability to precisely control the magnetoresistive stripe and throat heights. In one embodiment, additional guide rails are disposed along the outer edges of the slider ABS to facilitate maintaining slider symmetry during the lapping process and prevent the slider from canting to one side. The sacrificial extension and the guide rails are partially or completely removed during the lapping process. The shape of the sacrificial extensions may be optimized for the various embodiments.
In another embodiment, the sacrificial extension is formed with a cross-sectional shape having a narrow neck which encourages breakage during the ABS lapping process, thus, further accelerating the process. In another embodiment, a channel is disposed on the side of the slider opposite the ABS to provide space for the sacrificial extension of the adjacent slider and allow the sliders to be spaced closer together on the wafer surface for more efficient use of the wafer during head fabrication.